(InxGa1-x)2O3 Thin Film Based Solar-Blind Deep UV Photodetectors with Ultra-High Detectivity and On/Off Current Ratio

This work reports the fabrication of high performance solar-blind deep-UV photodetectors using (InxGa1-x)(2)O-3 thin films grown on Al2O3 (0001) substrates. The In contents in (InxGa1-x)(2)O-3 are controlled at x = 0, 0.1 and 0.2, whereas a higher In content leads to phase segregation of Ga2O3 and In2O3. The bandgaps of (InxGa1-x)(2)O-3 films are tuned from 4.93 eV for Ga2O3 to 4.67 eV for (In0.2Ga0.8)(2)O-3. Schottky-type photodetectors based on metal-semiconductor-metal structure were fabricated. The (In0.1Ga0.9)(2)O-3 photodetector is highly sensitive to solar-blind UV spectrum and achieves a large on/off current ratio of over 10(8), a remarkable specific detectivity of 4.5 x 10(16) Jones with a prominent responsivity of 23.3 A W--(1). Such enhanced performance compared to Ga2O3 is associated with In modulated optical and electronic properties. High-resolution X-ray photoemission spectroscopy was used to study the interfacial electronic structure at the semiconductor-metal interface. A large Schottky barrier height of 1.31 eV was found for (In0.1Ga0.9)(2)O-3 devices, accounting for the low dark current. More importantly, the incorporation of In introduces In 4d states hybridizing with O 2p at top of the valence band of (In0.1Ga0.9)(2)O-3, which increases the optical absorption to generate a higher density of photocarriers, and therefore results in greater photocurrents.